Exemplary embodiments of the invention generally relate to a rotary wing aircraft, and more particularly, to a de-rotation system for limiting rotation of a shaft fairing of the rotary wing aircraft.
The aerodynamic drag associated with a rotor hub of a rotary wing aircraft is a significant portion of the overall aircraft drag, typically 25 percent to 30 percent for conventional single-rotor helicopters. The rotor system drag increases for a rotary wing aircraft having a counter-rotating, coaxial rotor system primarily due to the dual rotor hubs and the interconnecting main rotor shaft assembly. For high-speed rotary wing aircraft, the increased drag resulting from the counter-rotating, coaxial rotor system may result in a relatively significant power penalty.
The aerodynamic drag of the dual counter-rotating, coaxial rotor system is generated by three main components—the upper rotor hub assembly, the lower rotor hub assembly, and the interconnecting main rotor shaft assembly. The drag contribution may be approximately 40 percent for each of the hubs, and 20 percent for the interconnecting main rotor shaft assembly. Typically, a rotor hub fairing arrangement is mounted to each of the upper rotor hub and the lower rotor hub such that overall drag on the rotorcraft is reduced. The interconnecting main rotor shaft between the upper rotor hub assembly and the lower rotor hub assembly, however, is typically exposed.